Half of those convicted of sex offences, violent crimes and burglaries escape jail, according to figures released by the Ministry of Justice.
More than 65,000 convicted criminals walked free last year despite being found guilty of serious offences including rape, sexual assault and robbery.
Of the 2,324 convicted of sexual assault, 49% did not receive a custodial sentence. In cases of sexual offences against children under the age of 13, nearly half - 46% - were not jailed.
The figures show that 49% of burglars and 40% of those convicted of robbery received non-custodial sentences, as did 51% of those convicted of possession of drugs with intent to supply.
The figures were released following a parliamentary question from shadow justice secretary Sadiq Khan, who told the Telegraph that they were an ‘insult to victims’.
Khan said: ‘Some of these crimes are so serious and violent that members of the public rightly expect them to lead to a prison sentence. Justice done on the cheap like this risks prisoners reoffending rather than being reformed, which means more victims and misery.’
Justice secretary Chris Grayling, said the government is overhauling sentencing guidelines to ensure the ‘toughest sentencing measures’ are available to the courts.
Prison reform campaigners accused politicians of presenting a misleading picture.
Frances Crook, chief executive of the Howard League for Penal Reform, said: 'It is disappointing that these statistics are being manipulated to stoke up fear.' Offences classed as serious might include 'a 15-year-old sleeping with his 14-year-old girlfriend, a "burglary" involving a homeless person getting into someone’s shed or a "child abduction" with a divorcee failing to return kids on time after an access visit,' she said.
'Prison is a simplistic answer in many cases,' she added. 'Police and judicial discretion are crucial within properly considered national guidelines. The truth is that the number of people behind bars has doubled in the past 20 years, with many people who have committed non-violent crimes being imprisoned needlessly.'